The present invention relates to a color image forming apparatus in which a photoreceptor is used as an image retainer for forming a toner image on its surface, and more particularly relates to an improvement in the workability of jam clearance and toner replenishment by replacing a process cartridge.
In a color image forming apparatus for which a photoreceptor is used, a plurality of developing units are disposed around the photoreceptor, that is, four developing units including toners of Y, M, C and black are respectively disposed close to the circumferential surface of the photoreceptor. Development operation is conducted in such a manner that the toners of primary colors of Y, M and C are superimposed when the photoreceptor is rotated by 3 revolutions (by 4 revolutions when black toner is included). Then the formed toner image is transferred onto a transfer sheet and thermally fixed by a fixing unit.
A photoreceptor drum or photoreceptor belt, which is an image forming body, composes a process cartridge together with a cleaner, charger, discharger and developing unit. In the case where a problem has occurred in the process of operation, the process cartridge is taken out from the image forming apparatus, so that inspection and jam clearance can be easily carried out. In spite of the above construction, inspection and jam clearance can not be competently carried out in the image forming apparatus of the prior art.
Further, the image forming apparatus of the prior art has the following disadvantages:
When the process cartridge and a unit composed of developing units are engaged with the image forming apparatus after they have been disengaged from it, they can not be smoothly connected with a drive system, and further it is difficult to conduct maintenance and jam clearance.